Lube extraction with an ethyl glycolate solvent

ABSTRACT

POLAR MATERIALS, SUCH AS HIGH MOLECULAR WEIGHT AROMATICS, ARE SEPARATED FROM PETROLEUM DISTILLATE FRACTIONS BY CONTACTING A PETROLEUM DISTILLATE FRACTION WITH A SELECTIVE EXTRACTION SOLVENT. THE SOLVENTS EMPLOYED, IN ACCORDANCE WITH THIS DISCLOSURE, ARE HYDROXY SUBSTITUTED ETHERS AND ESTERS. THE RESULTS OBTAINED WITH THESE SOLVENTS ARE COMPARED WITH THE RESULTS OBTAINED WITH THE USE OF PHENOL.

United States Patent 3,567,627 LUBE EXTRACTION WITH AN ETHYL GLYCOLATE SOLVENT John M. McDonald, 152 Norman St., and Charles C. Hong, 811 Devine St., Apt. 30, both of Sarnia, Ontario, Canada No Drawing. Filed Nov. 14, 1968, Ser. No. 775,942 Int. Cl. Clllg 21/16 US. Cl. 208-329 2 Claims ABSTRACT OF THE DISCLOSURE Polar materials, such as high molecular weight aromatics, are separated from petroleum distillate fractions by contacting a petroleum distillate fraction with a selective extraction solvent. The solvents employed, in accordance with this disclosure, are hydroxy substituted ethers and esters. The results obtained with these solvents are compared with the results obtained with the use of phenol.

BACKGROUND OF THE INVENTION This invention relates to a method of separating polar components from petroleum distillate fractions. More particularly, this invention relates to a method of selectively extracting the polar constituents from petroleum distillate fractions. Still more particularly, this invention relates to a liquid/liquid extraction process wherein certain slected solvents are used to extract polar components from petroleum distillate fractions. Yet more particularly, this invention relates to a process wherein hydroxy substituted ethers and esters and mixtures thereof are used to selectively extract polar constituents from petroleum distillate fractions.

It is well known in the art to contact petroleum dis tillate fractions with solvents having a preferential selectivity for the more polar components to thereby remove these components from the petroleum distillate fraction. For example, it is known in the art to use such solvents as phenol, furfural, sulfur dioxide, nitrobenzene, etc., for this purpose. Moreover, it is known in the art that several factors will influence the degree of separation which can be achieved with these solvents. By far the most significant of these factors are the relative selectivity of the solvent toward the more polar components and the ease with Which the selective solvent may be separated from both the polar components and the petroleum distillate frac tion. In addition to these, other factors are known to influence the relative success of a selective extraction process; e.g., the relative solubility of the oil in the solvent, the relative solubility of the polar constituents in the solvent, the number of theoretical plates needed to achieve the desired rafiinate quality, and the temperature at which the petroleum distillate fraction and the solvent are contacted. When considered in light of all of these factors, phenol is well known to yield the best overall results. Notwithstanding, the search has continued for even better selective solvents. For example, considerable effort continues to be devoted to the discovery of a selective solvent which is more selective than phenol.

SUMMARY OF THE INVENTION It has now been discovered that certain selective solvents, when used in accordance with this invention, are effective in removing the more polar constituents from petroleum distillate fractions, thereby improving the viscosity index, color, and oxidation stability of the petroleum distillate fraction. Accordingly, it is an object of this invention to provide a selective extraction process for the separation of the more polar constituents from a petroleum distillate fraction. Another object of this invention is to provide a selective extraction process for the separation of polar constituents wherein the loss of high viscosity index constituents is reduced. Still another object of this invention is to provide a selective extraction process for removing polar constituents from petroleum distillate fractions wherein the yield of useful petroleum product is increased. Other objects will be apparent from the following description.

According to this invention, the foregoing and other objects are accomplished by contacting a petroleum distillate fraction with certain selective solvents at conditions under which the more polar constituents of the petroleum distillate fraction are selectively extracted by the selective solvents. Moreover, the petroleum distillate fraction and the selective solvent will be contacted in such a manner as to insure good mixing, and hence, good contacting between the selective solvent and the polar constituents to be removed. The temperature at which the selective solvents and the petroleum distillate fraction are contacted should be such that the solvent (extract) phase and the petroleum distillate fraction (rafiinate) phase are maintained in the liquid state and both are immiscible. It will be appreciated that the operable range of temperatures can be extended, somewhat, by the use of pressure to maintain both phases in the liquid state.

DETAILED DESCRIPTION Essentially any petroleum distillate fraction containing polar materials may be upgraded by the method of the present invention. In general, however, the process of the present invention will be most useful for petroleum distillate fractions boiling between the range of 500 F. and 1500 F. This includes the lubricating and specialty oil fractions which are commonly improved by selective extraction of the polar constituents. The petroleum distillate fractions which may be treated by the method of this invention will have API gravities at 60 F. ranging between 10 and 40, pour points between and +180 F. and viscosities of F. between 30 and 10,000 SSU. These petroleum distillate fractions may be cut from crude oils obtained from essentially any source; e.g., crudes obtained from AMMCO, Kuwait, the Pan Handle, North Louisiana, Tia Juana, Western Canada, etc.

The solvents which may be used in the extraction process of the present invention are high boiling, high density, polar materials. More specifically, the solvents used in this invention are the hydroxy substituted ethers and esters containing between two and three carbon atoms between the hydroxy group and the ether or ester group, and having a molecular weight below about 200. Particularly preferred solvents which are used in the process of the present invention are Z-phenoxyethanol, ethyl glycolate and ethyl lactate. These solvents can be represented structurally as:

oo-o on II Et-O OCOH and respectively.

The petroleum distillate fraction and the selective solvent may be contacted in any suitable contacting apparatus which are well known in the prior art. It will be appreciated that good contacting is essential if the separation is to approach equilibrium. According, the apparatus employed should be designed such that the separation attained is comparable to that which could be obtained in a vessel having between 1 and 20 theoretical stages. Such separation can be attained in both batch and continuous equipment. For practical reasons, continuous operation will be preferred. In this type of operation, the selective solvent is generally introduced at or near the top of the contacting vessel and flows downwardly while contacting the petroleum distillate fraction. The solvent phase, enriched in polar constituents, is recovered from the bottom of the vessel and separated by conventional means such as distillation. The petroleum distillate fraction, on the other hand, is fed to the contacting apparatus at or near the bottom and flows upwardly. The thus treated petroleum distillate fraction, reduced in polar constituent content, is recovered from the top and entrained solvent is separated therefrom by conventional means such as distillation.

The liquid/liquid extraction process of the present invention is operable over a wide range of temperatures. It will be appreciated. however, that the range of operable temperatures will vary with the particular solvent employed. For example, as has already been pointed out, the solvent phase and the petroleum distillate fraction phase must be immiscible at the temperature employed. Moreover, it is essential that both phases be maintained in the liquid state during the contacting step. In general, the solvents of the present invention may be employed at temperatures between the range of about 100 and 300 F.; however, best results will be obtained at temperatures between the range of about 100 and 200 F.

In general, the process of this invention is operable over a wide range of solvent to distillate fraction ratios. In fact, some benefit will be realized at any solvent to distillate fraction ratio within the immiscibility region of the particular system. Notwithstanding, for practical reasons, the process will generally be operated at a solvent to distiallate fraction ratio between about 50 and 1000% on avolume basis.

The polar costituents which may be removed by the process of this invention are principally condensed aromatic components. In general, these materials will contain between about and 50 carbon atoms per molecule. It will be appreciated, however, that other polar materials may be separated by the process of this invention. These include both nitrogen and sulfur compounds which might be present in the petroleum distillate fraction. In general, the process of this invention can be used to remove polar component concentrations ranging as high as 80 Wt. percent of the petroleum distillate fraction. Best results, however, will be obtained when the concentration of polar components does not exceed 60 wt. percent.

The petroleum distillate fractions which are treated by the method of this invention will be substantially reduced in polar components, and hence, will exhibit improved viscosity indices, color and oxidation stability. Moreover, the petroleum distillate fractions treated by the method of this invention can be used as lubricating oils, diesel fuels, transformer oils, etc.

PREFERRED EMBODIMENT In a preferred embodiment of the present invention, lubricating oil fractions boiling between the range of 600 and 1100 F. will be treated with Z-phenoxyethanol at a temperature between 120 and 180 F. and a pressure between 1 and 2 atmospheres. The lubricating oil fraction and the phenoxyethanol will be contacted in an extraction unit having between 1 and 10 theoretical stages. The ratio of phenoxyethanol to lubricaitng oil fraction will range between about 1 and 4 on a volume basis.

The preferred embodiment is further illustrated by the following examples:

4 EXAMPLE 1 Thirty milliliters of a 10 grade Western Canadian lube distillate having the following inspections:

API gravity at 60 F.: 28.6

Pour point: F.

Viscosity at 210 F.: 42.5 SUS Refractive index at 60 C.: 1.4796 Dewaxed viscosity index (0 F. pour): 60

were solvent extracted by contacting with 30 milliliters of 2-phenoxy-ethanol in a batch extractor at a temperature of 140 F. and a pressure of 1 atmosphere. The mixture was well stirred to obtain optimum contacting and then allowed to settle. After settling, the solvent (extract) and lubricating oil (ratfinate) phases were separated, the solvent in each removed by distillation and the oil in each phase analyzed.

The raffinate phase contained 9.7 wt. percent solvent while the extract phase contained 92.0 wt. percent solvent. The oil in the rafiiniate phase had a refractive index of 1.4705 at 140 F. and a dewaxed viscosity index of 72.1. The oil recovered from the extract phase was very aromatic and had a refractive index at 140 F. of 1.5510.

In the same manner batch extractions were carried out at 140 on the distillate to which certain amounts of saturated and aromatic fractions had been added. These saturated and aromatic fractions were obtained by fractionation of the distillate itself and were used to vary the refractive index and viscosity index of the feed distillate. The raflinate and extract phases were analyzed as above and a ternary composition diagram for the distillate and Z-phenoxyethanol constructed by the method of Hunter and Nash (T. G. Hunter and A. W. Nash, Ind. Eng. Chem, 27, 836 (1935).)

By means of established correlations between batch extractions and continuous counter-current processes it can be predicted from the ternary diagram that in a continuous counter-current process an oil of viscosity index may be obtained from the 10 grade feed distillate by extraction with Z-phenoxyethanol in 80 wt. percent yield in 5 ideal stages rising a solvent to oil ratio of 2.0 on a volume basis.

EXAMPLE 2 To further illustrate the improved yield obtained with the solvent of this invention the extraction of the 10 grade lube distillate with phenol at 140 F. was investigated in the same experimental manner as in Example 1. At a temperature of 140 F. and a solvent to oil ratio of 1.6 (volume basis) the 90 viscosity index product oil is obtained in only 65 wt. percent yield with phenol as the extraction solvent in 3 ideal stages.

EXAMPLE 3 To further illustrate the preferred embodiment of this invention 30 milliliters of a 30 grade Western Canadian lube distillate having the following inspections:

API gravity at 60 F.: 23.0

Pour point: F.

Viscosity at 210 F.: 75 SUS Refractive index at 60 0.: 1.4943

Dewaxed viscosity index (+25 F. pour): 56

were solvent extracted by contacting with 30 milliliters of Z-phenoxyethanol in a batch extraction unit at 180 F. and a pressure of 1 atmosphere. The mixture was well stirred to obtain optimum contacting and then allowed to settle. After settling, the solvent (extract) and lube oil (raffinate) phases were separated, the solvent in each removed by distillation and the oil in each phase analyzed.

The rafiinate phase contained 10.1 wt. percent solvent while the extract phase contained 89.0 wt. percent solvent. The oil in the rafiinate phase had a refractive index at F. (60 C.) of 1.4834 and a dewaxed viscosity index of 73.3. The oil recovered from the extract phase was very aromatic and had a refractive index at 140 F. of 1.5570.

In the same manner batch extractions were carried out at 180 F. on the distillate to which certain amounts of saturated and aromatic fractions had been added. These saturated and aromatic fractions were obtained from the distillate itself and were used to vary the refractive index and viscosity index of the feed distillate. The raffinate and extract phases were analyzed as above and a ternary composition diagram for the distillate and 2-phenoxyethanol constructed by the method of Hunter and Nash.

By means of established correlations between batch extractions and continuous counter-current processes, it can be predicted from the ternary diagram that in a continuous counter-current process an oil of 90 viscosity index may be obtained from the 30-grade feed distillate by extraction with 2-phenoxyethanol in 71 wt. percent yield in 4 ideal stages using a solvent to oil ratio of 2.0 on a volume basis.

The extraction of this 30 grade distillate with phenol at a temperature of 180 yields the 90 viscosity index product in only 47 wt. percent yield using 3 ideal stages and a solvent to oil ratio of 1.6 on a volume basis.

EXAMPLE 4 To further illustrate the present invention the extraction of the grade lube distillate having the inspections set forth in Example 1 was carried out using ethyl glycolate as the solvent. 30 milliliters of the lube distillate and 30 milliliters of ethyl glycolate were mixed well at 140 F. to ensure optimum contact. The mixture was then allowed to settle and the two phases separated. The raffinate (oil-rich) phase contained 13.9 wt. percent of the solvent and the extract (solvent-rich) phase contained 91.2 wt. percent solvent. The ratfinate oil had a refractive index at 140 F. of 1.4734 and a dewaxed viscosity index of 69. The extract oil had a refractive index at 140 F. of 1.5210.

Batch extractions were carried out on the distillate to which certain amounts of aromatic and saturated fractions obtained from the distillate had been added as in Example 1. From these extraction data a ternary composition diagram for the 10 grade distillate and ethyl glycolate was constructed.

By means of the established correlation it is shown from the ternary diagram that in a continuous countercurrent extraction process a product oil of 90 viscosity index is obtained in wt. percent yield in 5 ideal stages at a solvent to oil ratio of 3.0 on a volume basis.

EXAMPLE 5 To further illustrate the present invention the extraction of the 10 grade lube distillate having the inspections set forth in Example 1 was carried out using ethyl lactate as the solvent. 30 milliliters of the lube distillate and 30 milliliters of ethyl lactate were mixed well at 140 F. The mixture was then allowed to settle and the two phases separated. The raflinate (oil-rich) phase contained 11.6 wt. percent solvent and the extract (solvent-rich) phase contained 90.5 wt. percent solvent. The rafiinate oil had a refractive index at 140 F. of 1.4734 and a dewaxed viscosity index of 69. The extract oil had a refractive index at 140 F. of 1.5200.

Batch extractions were carried out on the distillate to which certain amounts of aromatic and saturated fractions, obtained from the distillate, had been added as in Example 1. From these extraction data a ternary composition diagram for the 10 grade distillate and ethyl lactate was constructed.

By means of the established correlation it is shown from the ternary diagram that in a continuous counter-current extraction process a product oil of viscosity index is obtained in 72 wt. percent yield in 4 ideal stages at a solvent to oil ratio of 2.5 on a volume basis.

What is claimed is:

1. A process for extracting liquid polar materials selected from the group consisting of condensed aromatic components, sulfur and nitrogen compounds from a petroleum distillate fraction with ethyl glycolate in the liquid phase, recovering an extract phase enriched in polar component composition and a raffinate phase containing the petroleum distillate fraction with a reduced polar component concentration.

2. The process of claim 1 wherein said petroleum distillate fraction has a boiling range between about 500 and 1100 F.

References Cited UNITED STATES PATENTS 2,176,746 10/1939 Pokorny et a1. 208-334 2,343,611 3/1944 Cope et al 208-333 2,646,387 7/1953 Francis 208-333 HERBERT LEVINE, Primary Examiner US. Cl. X.R. 

